Modern helmets used in playing football, riding motor cycles, and etc. have a hard plastic outer shell. Inside there is webbing or relatively hard foam padding connecting the shell to the user's head. When there is a sudden and severe impact on the shell, the shell acts to protect the head from penetrating wounds and scrapes. However, the force is transmitted through the shell to the webbing or padding. Because the webbing or padding is relatively inflexible, they in turn transmit much of the force to the head.
The brain is resting somewhat loosely inside the skull. The sudden force applied to the skull from one direction causes the brain to strike the interior of the skull on the side opposite from where the force was applied. A single such blow can cause a concussion. Repeated strikes, even if not large enough to cause a concussion, are believed to lead to chronic traumatic encephalopathy (“CTE”).
US2013/0254978 of McInnis et al. discloses an insert inside a hard plastic shell of a helmet. The insert comprises a shock absorbing portion and a flexible liner portion. The shock absorbing portion is disposed between the helmet shell and the liner portion. The shock absorbing portion has a substantially constant resistive deformation force characteristic for reducing the peak G-force applied to the head during an impact.
The McInnis insert can comprise a plurality of flexible liner connectors for movably interconnecting the liner portion to a helmet shell to allow for the flexible movement of the liner portion relative the shell. The liner connectors can be in the form of vent shaft walls that each defines a vent shaft for providing fluid communication between a head space of the liner and an outer side of the shock absorbing portion to ventilate the space between the wearer's head and the interior of the helmet.
U.S. Pat. No. 8,918,918 of Jackson is basically directed to preventing neck injuries and concussions by using straps to attach a helmet to an anchor assembly at the shoulders, chest and upper back. Similarly, US Published Application No. 2015/0128332 of Jinkins includes shoulder flange straps to prevent the helmet from moving with respect to the shoulders.